1. Field of the Invention
The present invention relates to a private line connection controlling method in a fixed-length cell handling-type exchange that can set private line connection between specific subscriber terminals (hereinafter referred to as an ATM exchange) and a fixed-length cell handling-type exchange.
2. Related Art
FIG. 29 is a block diagram illustrating the configuration of a general ATM exchange which handles fixed-length cells. As shown in FIG. 29, the ATM (Asynchronous Transfer Mode) exchange 1 accommodates a plurality of subscriber terminals 2 and is mutually connected to other ATM exchanges (other stations) 1A and 1B. The ATM exchange 1 exchanges data between subscriber terminals 2 accommodated in the local station (ATM exchange 1) as well as data between other stations 1A and 1B.
More specifically, the ATM exchange 1 (or 1A, 1B) is generally an exchange that handles cell data with a fixed length (normally, data of 53 bytes formed of a header of 5 bytes and a data part of 48 bytes) called an ATM cell transmitted or received between subscriber terminals 2 (or ATM exchanges 1A, 1B). Each ATM cell can be asynchronously delivered (or exchanged) according to the header added to each ATM cell to transferred sites.
For that reason, the ATM exchange 1 (or 1A, 1B), as shown in FIG. 29, includes usually an ATM switch 3, a main control device (CC) 4 that performs various controls in the ATM exchange 1 (or 1A, 1B) including the ATM switch 3, a main storage device (MM) 5 that holds software for the main control device 4, a line interface device (DS3: Digital Signal Level 3) 6, middle-rate interface shelves (MIFSH) 7, optical line interface devices (OC3c: Optical Carrier 3 concatenated) 8, high-rate interface shelf (HIFSH) 9, and an optical line interface devices (OC12c: Optical Carrier 12 concatenated) 10.
In concrete, the ATM switch 3 selects automatically a transfer route for an ATM cell according to tag information (routing information such as transfer destination address) set in the header of the ATM cell input. Here, the ATM switch 3 has three switch stages 3A to 3C. For example, as shown in FIG. 30, eight switching units 31 for 20 Gbps each that can accommodate eight 2.4 Gbps lines are arranged in the first switch stage 3A. Four switching units 32 for 40 Gbps each that can accommodate sixteen 2.4 Gbps lines are arranged in the second switch stage 3B. Eight switching units 31 for 20 Gbps are arranged in the third switch stage 3C, like the first switch stage.
In such a configuration, in the ATM switch 3, the tag information set in a binary form within the header of an input ATM cell is sequentially read bit by bit by means of the switching units 31 and 32 in each of the switching stages 3A to 3C. Then the ATM cell transfer route is automatically selected by repeating a selecting operation of "1" or "0".
The line interface device (DS3) 6, the middle-rate interface shelves (MIFSH) 7, the optical line interface devices (OC3c) 8, the high-rate interface shelf (HIFSH) 9, and the optical line interface devices (OC12c) 10 standardize each line rate to the ATM switch 3 to 2.4 Gbps because the line rate in the ATM switch 3 is 2.4 Gbps, as described above.
For example, if it is assumed that the line interface device (DS3) 6 (or the optical line interface device (OC3c) 8) is an interface that can accommodate lines corresponding to about 155 Mbps and that the middle-rate interface shelf (MIFSH) 7 is an interface that can accommodate lines corresponding to about 2.4 Gbps, and that the line rate between subscriber terminals 2 and the ATM switch 3 is about 44 Mbps, the line interface device (DS3) 6 (or the optical line interface device (OC3c)8) accommodates three lines (44 Mbps.times.3). Further, as shown in FIG. 31, each line rate to the ATM switch 3 can be standardized to about 2.4 Gbps by accommodating sixteen lines (155 Mbps.times.16) in the middle-rate interface shelf (MIFSH) 7.
In contrast, the optical line interface device (OC12c) 10 is an interface that can accommodate lines corresponding to about 622 Mps. The high-rate interface shelf (HIFSH) 9 is an interface that can accommodate lines corresponding to about 2.4 Gbps. In this case, when the line rate between the subscriber terminals 2 and the ATM switch 3 is about 44 Mbps, each line rate to the ATM switch 3 can be standardized to about 2.4 Gbps by accommodating twelve 44 Mbps-lines (44M bps.times.12) in the optical line interface device (OC12c) 10 and accommodating four lines (622 Mbps.times.4) in the high-rate interface shelf (HIFSH) 9, as shown in FIG. 32.
That is, the ATM exchange 1 can perform a high-rate exchange process to the low-rate ATM cells by multiplexing a predetermined number of ATM cells from each subscriber terminal 2 or other stations 1A and 1B in each interface thereof and then standardizing and converting the transfer rate of all the ATM cells input to the ATM switch 3 (lines accommodated in the ATM switch 3) into a high transfer rate of 2.4 Gbps.
The other ATM exchanges 1A and 1B have the configuration equivalent to that of the ATM exchange 1. However, they use different interfaces according to the transfer rate of an ATM cell handled (the transmission rate of an accommodated line). For example, as shown in FIG. 29, the other exchange 1A uses an optical line interface device (OC3c) 8 and a middle-rate interface shelf (MIFSH) 7 to accommodate the middle-rate (155 Mbps) line while the other exchange 1B uses a high-rate interface shelf (HIFSH) 9 and an optical line interface device (OC12c) 10 to accommodate the high-rate (622 Mbps) channel.
When accommodating only middle-rate (155 Mbps) channel, the ATM exchanges 1, 1A or 1B, for example, as shown in FIG. 33, uses only the optical line interface devices (OC3c) 8 and the middle-rate interface shelves (MIFSH) 7, whereby they are mutually connected via the interfaces.
In FIG. 29, numeral 11 represents an Ethernet control device (ETC). Numeral 12 represents a maintenance and operation management control device (OMP). The Ethernet control device 11 controls a device connected to the Ethernet network 13. The maintenance and operation management control device 12 informs the Ethernet control device 11 in response to a maintenance and operation command from a maintenance personnel) operator of the ATM exchange 1. As shown in FIG. 29, various controls such as operation and maintenance of the ATM exchange 1 are performed via the Ethernet network by connecting the main control device 4 in the ATM exchange 1 via the Ethernet control device 11 and the Ethernet network 13.
As an example of such a control, for example, it may be considered that a private line (PVC: Permanent Virtual Channel) connection is set between subscriber terminals 2 accommodated in the ATM exchange 1. First, the operator of the ATM exchange 1 issues the connection request command 14 of a PVC having the format, e.g. shown in FIG. 34, from the maintenance and operation management control device 12 to the main control device 4 of the ATM exchange 1 via the Ethernet control device 11 and the Ethernet network 13 at a PVC path setting time.
The PVC connection request command 14 stores various kinds of information including service type (PVC connection), the location of each subscriber terminal 2 on an originating side/destination side, telephone number of each subscriber terminal 2 of an originating side/destination side, a virtual route identifier (VPI: Virtual Route Identifier) of an originating side/destination side, and a virtual channel identifier (VCI: Virtual Channel Identifier) of an originating side/destination side and the like.
When receiving the PVC connection request command 14, the main control device 4 analyzes main information contained in the command 14 and then informs the interface shelf 7 or 9 of routing information regarding the path on which a PVC is set based on VPI and VCI, via the ATM switch 3. Thus, the cell transfer route is fixed by rewriting tag information on an ATM cell passing the ATM switch 3 so that a PVC path using a path designated with VPI and VCI is set between the corresponding subscriber terminals 2.
However, in the ATM exchange 1 described above, since the PVC path connection can be achieved (set) only when an operator inputs a PVC connection request command, an operator which operates the maintenance and operation management control device 12 must be stationed all the time at a PVC path setting time in, for example, nighttime and holidays.
When an operator inputs a PVC connection request command, the PVC route cannot be set if the band of a route designated by the VPI and VCI is not left more than a using band.